Agreed, CoD4 is my favorite as well.
This game is actually a challenge to me sometimes due to all of the noobs/aggravating campers moving to Mw2 and the good/pros still playing CoD4. I either see people quick scoping, or rushing and drop shotting with there gun, much more competitive.
W@W is my favorite, to be fair I only played COD4 briefly but I did like it. I just think World at War had a lot more to offer in terms of game modes and replayability. I also really enjoyed the artistry of the maps